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Anosmia
Mohammed alqabasani R 5
Rhinology research chair academic activity
13-11-2013
King saud university
Rhinology Chair
Rhinology research Chair Weekly Activity
The chemo senses of smell and taste contribute to quality of life and environmental appreciation they also play significant role nutrition and safety.
Disorders of olfaction are common worldwide and may involve as many as 2 to 4 million people in the United States
anatomy
► the nasal passages
contain the structures of olfaction which include:
► the upper nasal septum , middle and superiorturbinates.
► These structures facilitate airflow and contain the primary olfactory neurons
anatomy
► In the olfactory mucosa,
the axons from the bipolar olfactory neurons coalesce
into bundles to form cranial nerve I
This nerve traverses upward through the cribriform
plate and skull base to the olfactory bulb to cortex
histology
►The olfactory epithelium is primarily composed of pseudostratified columnar-type epithelium
situated with a vascular lamina propria, and lack a submucosa.
► It is derived from ectoderm
► It can regenerate after damage but it rarely complete also it depend on degree of damage
Histology
►The human olfactory epithelium covers an area of roughly 1 cm2 on each side
► Humans have approximately 6 million olfactory neurons each cell express single odorant receptor
histology
►The cells that facilitate olfaction are divided into 4 main cell types:
1-ciliated olfactory receptors.
2-microvillar cells.
3-sustentacular cells.
4- basal cells.
Nerves involve in smell
►Cranial nerve I mediates the olfactory response
►The trigeminal nerve relays irritating odors such as carbon dioxide and ammonia
►Cranial nerves IX and X assist in retronasal olfaction
►Most patient-described losses or
disturbances of taste are olfactory losses.
►True solitary taste loss is less common
Taste
► Grossly, the tongue is composed of multiple taste papillae geographically distributed:
Fungiform,circumvallate and foliate
papillae which contain taste
buds that facilitate gustatory sensation
► The filiform papillas do not contribute to taste
PHYSIOLOGY OF SMELL
► Nasal airflow plays an integral part of smell detection.
► As airflow distributes itself in the nasal cavity, about 15% flows to the olfactory cleft
PHYSIOLOGY OF SMELL
► key to this process is that odorant
molecules must dissolve in or pass through the
mucous overlying the olfactory epithelium to be
detected. Once the odorants bind to the receptor
neurons, a complex enzyme-mediated pathway
Will start
PHYSIOLOGY OF TASTE
► In the taste buds, the chemical
molecules are transformed into electrical signals
that travel to the nucleus solitarius (medulla), to
the ventricular posterior medial nucleus in the thalamus then to the parietal lobe, and give the
perception of gustation
PHYSIOLOGY OF TASTE
► olfaction and food flavor perception is
retronasal olfaction, which occurs during
ingestion of substances with airflow of
odorant molecules generated by exhalation
or mouth and pharynx contraction.
DIAGNOSIS AND WORKUP OF OLFACTORYloss
► Hyposmia describes a decreased ability to
perceive smell
► Anosmia describes the absence of useful
smelling ability
► Parosmia is the distorted perception of
odor following a stimulus
► Phantosmia is perception of odor in the
absence of an odorant stimulus.
DIAGNOSIS AND WORKUP OF OLFACTORYloss
►History:
►age
►the onset, sudden vs gradual ,
►Side and duration of smell and taste changes.
►The patient may not disclose an olfactory disturbance unless directly asked.
DIAGNOSIS AND WORKUP OF OLFACTORYloss
►Any nasal symptoms should be addressed in details
►Associated clinical clues such as preceding trauma or viral infection ,exposure to toxin smoking
►Taste loss vs flavor
DIAGNOSIS AND WORKUP OF OLFACTORYloss
►Past surgical history:
Any nasal surgery
►Past medical: radiation ,delayed puberty ,dementia and neurological disease
►Detailed medication history
►Family history of anosmia
Physical Examination for Olfaction
► Complete head and neck examination with specific concentration on:
anterior rhinoscopy may reveal gross disease such as septal perforation, polyps, and epistaxis, tumors, or allergic edematous nasal mucosa
► nasal endoscopy, a view of the olfactory cleft and assessment of blockage
► Neurologic status and cranial nerve functionshould be assessed
► Documentation of the physical examination is vital beforesurgery.
Olfactory testing
►Is it important ? why ?
►1-to establish validity &nature of patient complaint
►2-to monitor the changes over time
►3-to detect malingering
►4-establish compensation for permanent disability
Investigation of anosmia
►Two classes of testing are available:
electro physical and psychophysical tests however psychophysical tests are more useful in the interoffice setting, more widely used.
►Olfactory testing generally measures either threshold of smell or identification of various smells
psychophysical tests
►Mostly common used test is UOPSIT (smell identification test ):
►Easy test can be finished in 15 minutes multiple language
►It has four booklets contain 10 odorant
►Stimuli are embedded 10-50 micro m diameter encapsulated crystals located on scratch and sniff strip
psychophysical tests
►UOPSIT (smell identification test ):► Over each strip mcq with four choices patient should choose answer even if
none seems appropriate or no odor perceived
► Then patient classified according their score to six groups :normosmia ,mild ,moderet, sever micosmia ,anosmia and malingering
► because chance performance is 10 out of 40 reflect avoidance which detect malingering patient
Investigation of anosmia
►Electrophysiological test
►1-odor event-related potential (OERPs):Which measure EEG from scalp electrode following presentation of odorant
It is good to detect malingering patient but can not be standardized
►Electro-olfactogram (EOG):Electrode inserted in olfactory cleft which measure the action potential it is no
good because of the difficulty in doing the test and its not reliable
Investigation
►Neuropsychological tests :
There is association between anosmia and neurodegenerative disease like Alzheimer's, dementia and Parkinson
So mini-mental state examination is easy screening tool if abnormal better to send the patient to neurologist for further assessment
Investigation of anosmia
► the history, physical examination, or olfactorytests suggest polypoid or obstructive disease ormalignant potential, then sinonasal imaging isComputed tomography (CT) scans of pns is needed
►Magnetic resonance imaging (MRI):may visualize the olfactory sulci and brainstructure
Common Causes of Olfactory Loss
►Olfactory disturbances can be
better separated into those with a conductive
component (anatomic blockage of the olfactory
cleft or surrounding structures) and a sensorineural
component (a nerve loss or damage to receptor
or higher cortical processing).
Common Causes of Olfactory Loss
►Nasal inflammatory disease:
nasal disorders from chronic rhinosinusitis to
polyps or allergic edema.
This group of disorders
is thought to primarily alter nasal airflow to the olfactory cleft
Common Causes of Olfactory Loss
► After Upper Respiratory Infection:
► Many patients report temporary decreased smell during upper respiratory infection (URTI) The nasal membrane edema commonly abates within a few days and smell returns to baseline.
However in a subset of patients, there is permanent loss and the prognosis is principally poor, with only one-third recovering
► In these patients a sensorineural insult occurs to
the primary olfactory neurons more in female
Causes of Olfactory Loss
►Head Trauma and Loss of Smell
► About 5% to 10% of patients with head trauma
suffer from smell loss, often from occipital or
frontal blows of the cribriform plate injury to the
olfactory bulb,or supraorbital and frontal brain
contusions that result in axonal injury.
Causes of Olfactory Loss
►Aging and Loss of Smell
sense of smell has been studied and defined
with age-related norms and known decreases
especially in individuals more than 65 years of age.
Causes of Olfactory Loss
►Congenital Loss of SmellThe cause is secondary to degeneration or failure of formation of the
olfactory bulb and/or epithelium during development
These patients often present around 8 years
► Kallman syndrome or hypogonadotropic
Hypogonadism the most common one
Causes of Olfactory Loss
►Toxins and Loss of Smellis best described as a sensorineuralInjury
It representbetween 1% and 5% of olfactory Disorders
The diagnosis is largely based o history and known
environmental exposure to the toxin.
Causes of Olfactory Loss
►Neoplasm and Loss of Smell
intracranial meningiomas, gliomas, and other
tumors may cause confined destruction of the
central olfactory neurons.
The intranasal tumors most frequently encountered are inverting papillomas, adenomas, squamous cell
carcinomasand esthesioneuroblastomas.
Causes of Olfactory Loss
► Postsurgery Loss of Smell:
If surgeons do not test and document olfactory loss at baseline they can miss a loss before surgery
Mechanism for loss post surgical intervention:► 1. Scar tissue► 2. Granulation tissue► 3. Persistent mucosal edema► 4. Inflammation and olfactory neuroepithelialdamage
Postsurgery Loss of Smell
►Middle turbinate resectionKimmelman1 suggested that a resection of thelower half of the middle turbinate likely doesnot result in anosmia or hyposmia
► study completed by Biedlingmaierand colleagues82 reviewed patients with partialmiddle turbinate resections during routine sinussurgery. They found that only 1 patient outof 198 (0.9%) complained of anosmia
Postsurgery Loss of Smell
► Septoplasty complications:
Overall, olfactory dysfunction after surgery is rare
after septoplasty One study found that total
anosmia following septoplasty in the long term
was found in 0.3% to 2.9% and hyposmia 1%.
► However, olfactory disturbance may be present
in up to 8% of patients before septoplasty, and
both the surgeon and patient may be unaware
without preoperative testing.
Postsurgery Loss of Smell
►Rhinoplasty complications:
Smell dysfunction following rhinoplasty has been reported and studied
► This suggests a low risk overall
(3%), but that it is nonetheless a risk that needs to be addressed with patients.
Postsurgery Loss of Smell
Skull base surgery and loss of smell:
Complex anterior and middle fossa skull base
surgery and many cranial surgeries near the
olfactory bulbs may cause olfactory loss
Causes of Olfactory Loss
► Neurodegenerative Disorders and Loss of Smell:
Much research has recently been devoted to the link between olfactory loss and neurodegenerative disorders such as Alzheimer disease and Parkinson Disease
Psychiatric Disorders (Depression or Anxiety)and Loss of Smell
TREATMENT OF OLFACTORY LOSS
►A patient’s quality of life is affected after an olfactory loss, from enjoying a meal to safety around toxic chemicals
►Determining the cause of the olfactory
deficit is imperative in counseling the patient and
predicting the likelihood of improvement
TREATMENT OF OLFACTORY LOSS
► Sensorineural losses are less likely to recover,
Whereas conductive losses, for example obstructive
nasal polyps, are more easily treatable
TREATMENT OF OLFACTORY LOSS
► Conductive smell losses resulting in hyposmia
or anosmia after nasal surgery or obstructing
URIs have treatments available
Nasal treatments:
including saline irrigations and a nasal steroid
spray, may decrease nasal membrane edema,
increase nasal airflow, and improve olfaction
TREATMENT OF OLFACTORY LOSS
► Medicines such as high
dose oral steroid boluses tapered over 3 weeks
have been studied with promising results.
recent study noted that a systemic steroid administration is
useful in distinguishing betweena conductive loss that will
improve and a sensorineuralloss that will not respond
TREATMENT OF OLFACTORY LOSS
►training the hyposmic or anosmic
patient to appreciate remaining sensory
modalities such as texture of food, residual
taste,and mouth feel is beneficial.
TREATMENT OF OLFACTORY LOSS
► Protection remains a critical aspect of smell Loss
Educating patients’ family members
► Patients with olfactory loss must use smoke
and natural gas detectors in their homes and offices.
► Converting to an electric powered system
may be safer.